The widespread use of cellular telephones, pagers, personal digital assistants (PDAs) and other wireless devices has adversely affected group events attended by people who use these devices. For example, attendees of large professional conferences often must deal with presentations being interrupted by cellular telephones ringing or pagers and personal digital assistants (PDAs) going off. This detracts from the overall effectiveness of the presentation while simultaneously annoying other attendees.
This problem occurs in other settings as well. At a movie theater, a person carrying a cellular telephone is a likely disturbance. When the cellular telephone rings, the remaining theater goers are disturbed. Even if the owner leaves the movie theater to take the call, in the process of leaving the theater, the owner distracts and blocks the view of others.
An almost infinite number of similar scenarios may occur, where wireless devices interrupt proceedings in a wide variety of settings, such as theaters, concert halls, restaurants, meeting rooms, hospitals, and other similar public venues.
In general, this problem persists in our culture not because people refuse to respect others, but rather because they simply forget to switch their devices to a non-intrusive or silent mode of operation. Wireless devices have become so commonplace that people often forget they have them.
As the widespread use of wireless devices has occurred only within the last several years, little effort has been put into preventing these devices from interrupting group events. Most of the attempts have been of the extremely “low tech” variety. Perhaps the first and simplest attempts have been the use of signs outside meeting areas or reminders given at the beginning of movies or presentations. These attempts have perhaps had a small degree of success; but surely, the situation will not improve as the number of wireless device users continues to grow.
Another solution is to use a jamming transmitter. Jamming transmitters for this type of application will typically have several independent oscillators from which jamming signals can be generated to block the use of certain frequency ranges. These types of jamming transmitters are often referred to as “barrage jammers.” The frequency ranges targeted are those used by paging devices as well as those used for call establishment by cellular/personal communication systems (PCS) systems. Thus, when activated in a designated area, a barrage jammer will prevent all pagers and mobile phones located in that area from receiving and transmitting calls by means of radio frequency (RF) interference. Barrage jammers typically have poor frequency selectivity which leads to interference with a larger frequency bandwidth than that used by pagers and cellular/PCS systems.
Barrage jammers might be implemented without the cooperation from cellular/PCS providers, so long as there are adequate guard bands available. However, once jamming begins, counter-jamming may result, either by deliberate action of providers, or more likely by autonomous response of power control systems within the PCS/cellular systems.
Another concern with barrage jammers is that they increase the RF noise floor in areas adjacent to their area of use. Many cellular/PCS systems are required to work in all types of buildings under very low signal conditions, and the use of barrage jammers in the same band and vicinity, results in an increase in the noise floor that could mean the difference between receiving and not receiving a critical call. Due to these limitations, as well as others, barrage jammers are not particularly well suited to addressing the problem at hand.
Yet another solution is referred to as an intelligent cellular disabler. Unlike barrage jammers, intelligent cellular disablers do not transmit an interference signal on the control channels. Rather, an intelligent cellular disabler, when located in a designated “quiet” area, functions as a detector. An intelligent cellular disabler will have a unique identification number for communicating with the cellular network. When an intelligent cellular disabler detects the presence of a mobile phone in the quiet area, the intelligent cellular disabler communicates the presence of the mobile to the cellular network which in turn prevents the authorization of call establishment. This, in effect, filters calls to mobiles through software.
Since an intelligent cellular disabler is a software-based solution, calls may be routed to the call recipient's voice mail box, provided they subscribe to a voice mail service. Similarly, the detector may exempt users who have designated emergency status. These users must preregister their phone numbers with the service providers. Thus, when an incoming call arrives, the detector recognizes the number and the call is established for a specified maximum duration, e.g., two minutes. Users are also permitted to make outgoing calls routed to “911” type services.
Unlike barrage jammers, intelligent cellular disablers, being an integral part of the cellular/PCS systems, must be provisioned by the cellular/PCS service providers or by a third-party working cooperatively with full support of the cellular/PCS service providers.
Yet another solution is referred to as an intelligent beacon disabler. Like intelligent cellular disablers, intelligent beacon disablers do not transmit an interference signal on the control channels. Intelligent beacon disablers are located in a quiet area and function such that any compatible wireless device in the quiet area is instructed to disable its ringer or disable its operation, while within the coverage area of the beacon. Obviously, only wireless devices which have a compatible receiver would respond to the beacon. The beacon receivers would typically be built on some technology other than cellular or PCS, such as wireless paging, Bluetooth, etc. The Bluetooth standard, promulgated by Bluetooth SIG, Inc. (“Bluetooth”) a not-for-profit trade association that promotes personal connectivity solutions based on the Bluetooth wireless technology. Accessible at the Internet address of www.bluetooth.org.
Intelligent beacon disablers do not cause interference or require any cooperation from cellular/PCS providers. However, intelligent beacon disablers do require compatible wireless devices. As such, effective deployment will be problematic for many years.
Yet another solution is referred to as a direct receive and transmit jammer. This type of jammer behaves like a small, independent and portable base station, which can directly interact intelligently or unintelligently with the operation of the local mobile phone. The jammer is predominantly in a receiving mode and will intelligently choose to transmit and block wireless devices if they are within close proximity of the jammer, thereby creating a quiet area.
This selective jamming technique uses a discriminating receiver to target the jamming transmitter. The benefit of such target selectivity is much less electromagnetic pollution in terms of raw power transmitted from and bandwidth used by the jammer. Therefore, this type of jammer is much less disruptive to passing traffic. The jammer only transmits long enough to prevent a cellular telephone from linking with the cellular/PCS network. Otherwise, no transmission occurs.
Selective jamming could be implemented without the cooperation of cellular/PCS providers, but could also negatively impact cellular/PCS operation. Like intelligent cellular disablers, this solution could be made to discriminate 911 calls and allow for “breakthroughs” during emergencies.
Still another solution uses electromagnetic interference (EMI) shielding. This solution uses EMI shielding techniques to make a room into what is known as a Faraday cage. Although labor intensive to construct, a Faraday cage essentially blocks, or greatly attenuates, virtually all electromagnetic radiation from entering or leaving the cage, that is, the quiet room.
With the current state of the art in EMI shielding techniques, and commercially available products one could conceivably implement a Faraday cage into the architecture of newly designed buildings for so-called “quiet conference” rooms. Unfortunately, all calls, including emergency calls, would be blocked, unless there were provisions to receive and decode emergency transmissions and then feed them through the cage to be retransmitted. Obviously this is an expensive and long term solution.
Governmental regulatory agencies may ultimately determine which one of these solutions is best to use or not to use. For example, in the United States, FCC Rule Part 15(5b) precludes the use of intentional interferers. Canada, the United Kingdom, Australia, France, and Japan all have similar prohibitions on jamming devices, although they are under evaluation in some countries.
It can thus be seen that, in light of current governmental regulations prohibiting the use of jamming devices, there is increasing need for a method of preventing the interruption of group events attended by people who use cellular telephones, pagers, PDAs, and other wireless devices.